The aroma of a fragrance or cosmetic can be classified roughly into a floral aroma and a fruity aroma and the floral aroma can be classified into three main floral aromas, that is, (1) muguet (lily of the valley), (2) rose, and (3) jasmine. Of these, an aroma having a muguet-like floral feeling is one of traditionally favored aromas and now it is a component used for imparting naturalness or flesh feeling to many products. Essential oil components can scarcely be obtained industrially from natural muguet, and thus, synthetic materials are used for the preparation of a muguet aroma.
As such an aroma having a muguet-like floral feeling, synthetic materials such as Lilial (Givaudan S.A.), Suzaral (Takasago International Corporation), Bourgeonal (Givaudan S.A./Quest), Mayol (Firmenich S.A.), Cyclamen aldehyde (Givaudan S.A.), 2,3-Dihydrofarnesal, and 2,3-Dihydrofarnesol have been used.
Of these synthetic materials, a racemic form of 2,3-dihydrofarnesal has already been organoleptically evaluated. A mixture of the (E)-isomer and the (Z)-isomer has a flower (floral) aroma note. The (E)-isomer of the racemic form has an aldehydic fragrance with a fresh floral aroma note and reminds of a lily of the valley or another flower. It is an aroma easily harmonizing with a fresh water note, an ozone note, a marine note or the like. On the other hand, the (Z)-isomer of the racemic form has aroma intensity slightly lower than that of the (E)-isomer and it provides an odor slightly inferior in freshness as a whole, but it is known to have an aroma showing similar olfactory characteristics (Patent Document 1).
Also, it is known that in the natural world, 2,3-dihydrofarnesal exists in plants and animals. For example, it is known that 2,3-dihydrofarnesal exists in an extract of Orchids (Aerides jarckanum), a flower aroma component of Citrus limon (Non-Patent Document 1) and a pheromone component of Bumblebees and Cuckoo Bumblebees (Non-Patent Document 2).
As an example of synthesizing optically active 2,3-dihydrofarnesal, a report on the synthesis of (3R)-2,3-dihydrofarnesal by asymmetric hydrogenation of (2E,6E)-farnesal is known (Non-Patent Document 3).